U.S. patent number 8,394,144 [Application Number 12/442,741] was granted by the patent office on 2013-03-12 for system for positioning of surgical inserts and tools.
This patent grant is currently assigned to Mazor Surgical Technologies Ltd.. The grantee listed for this patent is Eddie Batkilin, Leonid Kleyman, Eli Zehavi. Invention is credited to Eddie Batkilin, Leonid Kleyman, Eli Zehavi.
United States Patent |
8,394,144 |
Zehavi , et al. |
March 12, 2013 |
System for positioning of surgical inserts and tools
Abstract
A tracking and positioning system and method to enable the
precise positioning of an object or tool relative to its surgical
surroundings, and in accordance with preoperative CT images of the
operating site. When used for artificial spinal disc positioning,
the system comprises a computing system incorporating in memory the
preoperative CT data showing the two vertebrae and the
predetermined disc position between them; a 3-D target having
radio-opaque markers for attaching to one of the vertebrae to
define the position of the vertebra in an intra-operative
fluoroscope image of the spine; a tool for intra-operative
insertion of the artificial disc, and a registration system for
relating the intra-operative fluoroscope image to the preoperative
CT data, such that the predetermined disc position is displayed in
the fluoroscope image of the subject, thereby enabling the surgeon
to place the artificial disc accurately in its intended
position.
Inventors: |
Zehavi; Eli (Haifa,
IL), Kleyman; Leonid (Acco, IL), Batkilin;
Eddie (Nesher, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Zehavi; Eli
Kleyman; Leonid
Batkilin; Eddie |
Haifa
Acco
Nesher |
N/A
N/A
N/A |
IL
IL
IL |
|
|
Assignee: |
Mazor Surgical Technologies
Ltd. (Caesarea, IL)
|
Family
ID: |
39230675 |
Appl.
No.: |
12/442,741 |
Filed: |
September 25, 2007 |
PCT
Filed: |
September 25, 2007 |
PCT No.: |
PCT/IL2007/001192 |
371(c)(1),(2),(4) Date: |
March 25, 2009 |
PCT
Pub. No.: |
WO2008/038282 |
PCT
Pub. Date: |
April 03, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100030232 A1 |
Feb 4, 2010 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60846749 |
Sep 25, 2006 |
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60875561 |
Dec 19, 2006 |
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Current U.S.
Class: |
623/17.11;
606/130 |
Current CPC
Class: |
A61B
17/848 (20130101); A61F 2/4611 (20130101); A61B
34/10 (20160201); A61F 2002/4632 (20130101); A61F
2250/0098 (20130101); A61B 34/30 (20160201); A61B
2090/3966 (20160201); A61B 2090/376 (20160201); A61B
2034/104 (20160201); A61F 2002/3008 (20130101); A61B
90/11 (20160201); A61B 2090/363 (20160201); A61B
2090/364 (20160201); A61B 2034/105 (20160201); A61F
2/442 (20130101); A61B 2034/2068 (20160201) |
Current International
Class: |
A61F
2/44 (20060101) |
Field of
Search: |
;606/130,99,102,96,97,86R ;623/17.11-17.16
;600/407,424,425,426 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO03/105659 |
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Dec 2003 |
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WO |
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WO2005/032325 |
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Apr 2005 |
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WO |
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Other References
PCT Int'l Search Report dated Mar. 23, 2009 and Written Opinion of
the ISA, mailed Mar. 23, 2009 in PCT/IL2007/01192. cited by
applicant .
BrainLab AG of Feldkirchen, Gernany re computer aided system for
disc placement, Dec. 22, 2009. www.brainlab.com. cited by
applicant.
|
Primary Examiner: Robert; Eduardo C
Assistant Examiner: Negrellirodriguez; Christina
Attorney, Agent or Firm: Swirsky; Daniel J. AlphaPatent
Associates Ltd.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a U.S. National Phase Application under 35
U.S.C. 371 of PCT International Application No. PCT/IL2007/001192,
which has an international filing date of Sep. 25, 2007, and which
claims priority from U.S. Provisional Patent Application Nos.
60/846,749, filed Sep. 25, 2006, and 60/875,561, filed Dec. 19,
2006, all of which disclosures are hereby incorporated by
reference.
Claims
We claim:
1. A system for intraoperatively placing an artificial disc at a
predetermined position between two vertebrae of a subject, said
system comprising: a computing system having a storage medium
including a set of preoperative CT data showing said two vertebrae
and said predetermined position of said disc between them; at least
one three-dimensional target having radio-opaque markers adapted to
be attached to at least one of said vertebrae to define the
position of said vertebra in at least one intra-operative
fluoroscope image of the subject; a tool for intra-operative
insertion of said artificial disc; and a registration system for
relating said at least one intra-operative fluoroscope image to
said set of preoperative CT data, such that said predetermined disc
position is displayed in said at least one fluoroscope image of the
subject, thereby enabling intraoperative placement of said
artificial disc in said predetermined disc position.
2. A system according to claim 1 and wherein said predetermined
position of said disc is obtained from predefined geometrical
information about the position.
3. A system according to claim 1 and wherein said predetermined
position of said disc is obtained by adjusting said disc position
in a model obtained from said preoperative CT data, such that facet
joints between said vertebrae are in minimally stressed
positions.
4. A system according to claim 1 and further comprising at least
two pins attached to each of said vertebrae, each of said pins
comprising at least two radio-opaque markers disposed at known
positions along said pins, such that said pins define the
three-dimensional position of said vertebrae in said fluoroscope
images of the subject, such that said target may be removed to
allow intra-operative placement of said disc in said predetermined
position.
5. A system according to claim 1 and further comprising at least
one pin attached to each of said vertebra, each of said pins
comprising at least three radio-opaque markers disposed at fixed
positions along said pins, such that said pins define the
three-dimensional position of said vertebrae in said fluoroscope
images of the subject, such that said target may be removed to
allow intra-operative placement of said disc in said predetermined
position.
6. A system according to claim 1 and wherein said insertion tool is
either a manually operated tool or a robotically operated tool.
7. A system according to claim 1, wherein said at least one
three-dimensional target comprises at least two pins attached to
one of said two vertebrae, each of said at least two pins
comprising at least two radio-opaque markers disposed along their
length, such that the position of said vertebra is defined in at
least one intra-operative fluoroscope image of the subject.
8. A method of intraoperative positioning an artificial disc
between two vertebrae of a subject, said method comprising the
steps of: generating from a preoperative set of CT data, a CT model
showing said vertebrae; predetermining a position for said disc
between said vertebrae, and defining said position in said model;
attaching at least one three-dimensional target to one of said
vertebrae; generating at least one fluoroscope image of the
subject, such that the three-dimensional position of said one of
said vertebrae is defined in said at least one fluoroscope image by
means of said at least one target; registering said at least one
fluoroscope image of the subject with said CT model, such that a
rendering of said disc in its predetermined position is shown on
said at least one fluoroscope image; and using said at least one
fluoroscope image to position said disc intra-operatively such that
it can be disposed in said predetermined disc position.
9. A method according to claim 8 and wherein said artificial disc
is disposed in said predetermined disc position by ensuring that
said intra-operative position in said fluoroscope image essentially
coincides with said display of said predetermined disc
position.
10. A method according to claim 8 and wherein said predetermined
disc position is obtained from predefined geometrical information
about the optimum position.
11. A method according to claim 8 and wherein said predetermined
disc position is obtained by adjusting said disc position in said
CT model such that facet joints between said vertebrae are in
minimally stressed positions.
12. A method according to claim 8 and further comprising the steps
of: providing at least four pins, each of said pins comprising at
least two radio-opaque markers disposed at known positions along
their length; attaching at least two of said pins to each of said
vertebrae, such that said pins define the three-dimensional
position of said vertebrae in said at least one fluoroscope image;
utilizing the relationship between said known positions of said
target and said pins to compute a transformation between the
position of said target and said pins; and removing said target to
facilitate access to said vertebrae.
13. A method according to claim 8 and further comprising the steps
of: providing at least two pins, each of said pins comprising at
least three radio-opaque markers disposed at known positions along
said pins; attaching at least one of said pins to each of said
vertebrae, such that said pins define the three-dimensional
position of said vertebrae in said at least one fluoroscope image;
utilizing the relationship between said known positions of said
target and said pins to compute a transformation between the
position of said target and said pins; and removing said target to
facilitate access to said vertebrae.
14. A system for intraoperative placing an artificial disc at a
predetermined position between two vertebrae of a subject, said
system comprising: a computing system having a storage medium
including a set of preoperative CT data showing said two vertebrae
and said predetermined position of said disc between them; at least
one three-dimensional target having radio-opaque markers adapted to
be attached to at least one of said vertebrae to define the
position of said vertebra in at least one intra-operative
fluoroscope image of the subject; a jig adapted to be attached to
at least one of said vertebrae and supporting a reproducibly
alignable pointer; and a registration system for relating said at
least one intra-operative fluoroscope image to said set of
preoperative CT data, such that said predetermined disc position
and said pointer are displayed in said at least one fluoroscope
image of the subject, thereby enabling use of said pointer for
intraoperative placement of said artificial disc in its
predetermined position without the need to view a fluoroscope
image.
15. A system for intraoperatively inserting a surgical tool into a
predetermined position at a surgical site of a subject, said system
comprising: a computing system having a storage medium including a
set of preoperative CT data showing said surgical site and said
predetermined position of said surgical tool; at least one
three-dimensional target having radio-opaque markers adapted to be
attached to a feature of said subject at said surgical site to
define the position of said feature in at least one intra-operative
fluoroscope image of the subject; and a system for registering said
at least one intra-operative fluoroscope image to said set of
preoperative CT data, such that said predetermined position of said
surgical tool is displayed in at least one fluoroscope image of the
subject, thereby enabling intraoperative insertion of said surgical
tool into said predetermined position.
16. A system for intraoperatively placing an artificial disc at a
predetermined position between two vertebrae of a subject, said
system comprising: a computing system having a storage medium
including a set of preoperative CT data showing said two vertebrae
and said predetermined position of said disc between them; a tool
for intra-operative insertion of said artificial disc; a
registration system for relating said at least one intra-operative
fluoroscope image to said set of preoperative CT data, such that
said predetermined disc position is displayed in said at least one
fluoroscope image of the subject, thereby enabling intraoperative
placement of said artificial disc in said predetermined disc
position; and a set of pins for attaching to said two vertebrae,
said pins comprising a plurality of radio-opaque markers disposed
along their lengths, such that said pins define the
three-dimensional position of said two vertebrae in said
fluoroscope images of the subject.
17. A system according to claim 16 wherein said set of pins for
attaching to said two vertebrae comprises either of: at least two
pins attached to each of said two vertebrae, each of said at least
two pins comprising at least two radio-opaque markers disposed
along their length, or at least one pin attached to each of said
two vertebra, each of said at least one pin comprising at least
three radio-opaque markers disposed at known positions along its
length.
18. A system according to claim 16 wherein said predetermined
position of said disc is obtained from predefined geometrical
information about the position.
19. A system according to claim 16 wherein said predetermined
position of said disc is obtained by adjusting said disc position
in a model obtained from said preoperative CT data, such that facet
joints between said vertebrae are in minimally stressed
positions.
20. A system according to claim 16 wherein said set of pins for
attaching to said two vertebrae comprises at least one pin attached
to each of said two vertebra, said at least one pin being devoid of
protruding radio-opaque markers, and having a known orientation and
thickness, such that said pins define the three-dimensional
position of said two vertebrae in said fluoroscope images of the
subject.
21. A system according to claim 16 wherein said set of pins for
attaching to said two vertebrae comprises at least one pin attached
to each of said two vertebra, said at least one pin being devoid of
protruding radio-opaque markers, and having a known orientation and
shape, such that said pins define the three-dimensional position of
said two vertebrae in said fluoroscope images of the subject.
22. A system according to claim 16 wherein said set of pins for
attaching to said two vertebrae comprises at least 3 pins attached
to each of said two vertebrae, each of said pins comprising one
radio-opaque marker disposed along its length.
23. A method of intraoperative positioning an artificial disc
between two vertebrae of a subject, said method comprising the
steps of: generating from a preoperative set of CT data, a CT model
showing said vertebrae; predetermining a position for said disc
between said vertebrae, and defining said position in said model;
attaching a set of pins to said two vertebrae, said pins comprising
a plurality of radio-opaque markers disposed along their length;
generating at least one fluoroscope image of the subject, including
at least part of said two vertebrae and said pins, such that the
three-dimensional positions of said vertebrae are defined in said
at least one fluoroscope image by means of said pins; registering
said at least one fluoroscope image of the subject with said CT
model, such that a rendering of said disc in its predetermined
position is shown on said at least one fluoroscope image; and using
said at least one fluoroscope image to position said disc
intra-operatively such that it can be disposed in said
predetermined disc position.
24. A method according to claim 23, wherein said set of pins
attached to said two vertebrae comprises either of: at least two
pins attached to each of said two vertebrae, each of said at least
two pins comprising at least two radio-opaque markers disposed
along their length, or at least one pin attached to each of said
two vertebra, each of said at least one pin comprising at least
three radio-opaque markers disposed at known positions along its
length.
25. A method according to claim 23 and wherein said artificial disc
is disposed in said predetermined disc position by ensuring that
said intra-operative position in said fluoroscope image essentially
coincides with said display of said predetermined disc
position.
26. A method according to claim 23 and wherein said predetermined
disc position is obtained from predefined geometrical information
about the optimum position.
27. A method according to claim 23 and wherein said predetermined
disc position is obtained by adjusting said disc position in said
CT model such that facet joints between said vertebrae are in
minimally stressed positions.
Description
FIELD OF THE INVENTION
The present invention relates to the field of image reconstruction
for ensuring the correct placement of surgical implants and tools,
and especially to a system for ensuring correct surgical placement
of artificial spinal discs.
BACKGROUND OF THE INVENTION
The use of artificial discs in spinal surgery to restore spinal
mobility in patients with degenerative disc disease has been
practiced for several years as an alternative to spinal fusion, and
commercial systems for such disc replacement are available. The
artificial discs are generally made of a hard plastic material
which can pivot between two generally metal end plates attached to
the adjacent vertebrae. One of the problems associated with this
procedure is the need to insert the disc assembly into the correct
position between the two adjacent vertebrae, such that it provides
the correct pivoting action to the adjacent vertebrae. Since an
advantage of disc replacement over spinal fusion is the maintenance
of mobility, correct pivoting action is of great importance.
Located between and behind each pair of adjacent vertebrae, are the
facet joints, which are small joints which stabilize the segments
of the spine relative to each other, but nonetheless preserve the
flexibility needed to turn, bend, twist and generally ensure spinal
mobility. Reference is made to FIGS. 1A and 1B which illustrates
these facet joints 10, and the way in which, during spinal bending
forwards (FIG. 1A) and backwards (FIG. 1B), the facet joints are
stressed in one direction or the other. The arrows show the
direction of motion of the top facet for these two bending
situations. If the artificial disc is not accurately positioned,
the neighboring vertebrae will not maintain their correct mutual
positions, and undesired forces may be applied to the facet joints,
even when the patient is static. This situation becomes even more
aggravating in motion, when the facet joints have to operate
dynamically, and as the spine bends forwards or backwards,
excessive tension or thrust is put on the facet joints, generating
pain for the subject. In some cases, the pain limits subject
mobility to such an extent that spinal fusion occurs naturally, and
the spine loses its flexibility in that region. Malpositioning of
the disc may lead to sliding of the disk from it original location
due to excessive lateral forces acting thereon. This often requires
surgical revision and in some cases can cause severe nerve
damage.
The optimum disc position is generally taken to be laterally on the
midline of the vertebral body, and, at least as recommended for use
with the Charite.TM. Artificial Disc supplied by DePuy
International Ltd. of Leeds, U.K., 2 mm dorsal to the sagittal
vertebral midline. According to current practice, the disc
positioning is performed by the orthopedic surgeon by observing the
operating region in real time on a series of fluoroscope images
taken at different angles, generally laterally and A-P. The surgeon
estimates visually from the fluoroscope images when the disc is in
the optimum recommended position. However, this procedure may be
difficult to perform accurately since fluoroscope images may be
difficult to interpret clearly because of the large mass of
intervening soft tissue, and the desired midline positions cannot
be clearly delineated from these images. Furthermore, this
procedure involves a high radiation exposure, both to the patient,
the surgeon and the O.R staff.
Recently, a computer aided system for disc placement has been
described by BrainLAB AG of Feldkirchen, Germany, in which a
navigation system is adapted for use in defining the position of
the artificial disc in relation to the neighboring vertebrae. The
optical navigator uses sources or optical reflectors positioned on
the vertebrae themselves, and on the disc insertion tool in order
to relate the position of the disc to the vertebrae themselves.
This may well be an improvement over visual position estimating
methods, but it involves a complex navigation system, and
maintenance of clear lines of sight during the entire operation.
Since anterior access is used for these procedures, this may not be
a simple requirement to fulfill.
The placement of artificial Spinal replacement discs is only one of
a large number of surgical procedures in which objects have to be
accurately positioned within the body. Amongst such objects are
various other orthopedic implants, and surgical tools which have to
be accurately inserted into their destined location to perform
their intended task. Like disc replacement, such procedures are
often performed under minimally invasive conditions, where site
visibility or access is limited, thereby placing heavy reliance on
the experience and skill of the surgeon to ensure proper placement
of the object or tool.
There therefore exists a need for a surgical positioning system
which overcomes at least some of the disadvantages of prior art
systems and methods.
The disclosures of each of the publications mentioned in this
section and in other sections of the specification, are hereby
incorporated by reference, each in its entirety.
SUMMARY OF THE INVENTION
The present invention seeks to provide a new tracking and
positioning system and method to enable the precise positioning of
an object or tool relative to its surgical surroundings, and in
accordance with a preoperative plan of the surgical procedure, as
generally prepared using pre-operative CT images of the operating
site. The system is an Image Guided Surgery application which
increases the accuracy of such procedures in comparison with
methods previously used. The system and method are generally
described in this application for use in the positioning of
artificial disc inserts between the appropriate vertebrae of a
subject, though it is to be understood that the procedure is not
meant to be limited to this application but is applicable to any
such suitable surgical insertion and positioning procedure.
The spinal disc positioning embodiment of the present invention
uses a database of virtual implants, and allows preoperative
planning of the surgical procedure, including implant positioning
and spatial positioning and orientation of the surgical instrument
holder or guide. Based on the preoperatively scanned CT data, the
system generates a virtual model of the subject's spinal region
where the operation is to be performed, and enables the
determination of the optimum position of the disc on this model,
this being the preoperative planning. During the replacement
procedure, a registration process is performed between the
preoperative CT data, and the real time fluoroscope images, so that
the desired position of the disc, obtained from the preoperative CT
scans, can be projected onto the real-life fluoroscope image. The
surgeon can then position the real-life disc at the exact
predefined position using this fluoroscope image.
The alignment procedure of the CT image with the real time
fluoroscope images process cannot readily be performed using
vertebrally attached registration plates, since such plates, unless
mounted using a long holder that would then be prone to errors,
would obstruct the surgeon's limited field of view and freedom of
motion within the confines of the abdominal cavity where the
operation is being performed. The system therefore preferably uses
novel K-wires, or other types of surgical pins of similar function,
having a special design with fiduciary markers such as spheres
located on their shaft, and which are mounted on the vertebrae
adjacent to the disc insertion site. According to one preferred
embodiment, the special K-wires are registered with the
conventional target plate early in the procedure, such that the
target plate can then be removed and the tracking of the disc and
associated vertebrae continued using the special K-wires, which do
not impede the surgeon's view or actions.
According to a further preferred embodiment of the present
invention, it is also possible to perform the registration
procedure using only the novel K-wires but without using an
additional target plate at all. In this embodiment, use is
preferably made of at least two fiduciary balls on each of a pair
of K-wires mounted in a vertebra in order to define the vertebra's
position and orientation in three dimensions.
In the above described preferred embodiments, K-wires with
fiduciary marker balls on their shafts are used in order to define
the three-dimensional position of the vertebra. The use of spheres
on the shaft ensures an accurate and simple registration process,
since the center of a sphere has a well-defined and unique
position. However, it is to be understood that the invention can
also be implemented using regular K-wires, without any marker
balls, and wherein the registration routine utilizes the alignment
direction of the K-wires and their thickness in order to define the
three-dimensional position of the vertebra in which the K-wires are
stuck. This registration procedure may be more complex and possibly
less accurate than that using defined marker balls on the shafts,
but it does enable the use of standard components. In general, the
invention is not intended to be limited by the means by which the
registration is performed. Thus, for example, three K-wires in a
vertebra, each with one marker ball can also be used.
Throughout this application, the various embodiments using K-wires
are generally described in terms of the use of special K-wires
having marker spheres, since this is generally the most accurate
and simplest method to implement. However, wherever such special
K-wires are mentioned, it is to be understood that this is not
intended to be limiting, but is meant to include also other
registration procedures using regular K-wires as mentioned
hereinabove.
According to further preferred embodiments of the present
invention, it is also possible to perform the disc insertion
without removing the target plate, and hence without the use of any
K-wire markers. This embodiment provides a simpler registration
procedure, but can generally only be used where conditions are such
that the target plate can remain in situ without disturbing the
insertion procedure, and yet can still be used as a stable and
accurate spatial reference.
According to a further preferred embodiment of the present
invention, the optimum disc position is determined on the CT model
by adjusting the disc position in the preoperative planning phase
while viewing the spine kinematics and the effect of the disc
position movement on the facet joints of the neighboring vertebrae.
The optimum position and orientation is defined by that which
places the facet joints under the least strain or compression, both
with the spine static, and during motion.
According to a further preferred embodiment of the present
invention, the disc insertion can be performed using a surgical
robot. A particularly advantageous configuration is the use of a
miniature surgical robot, which can preferably even be bone-mounted
on a nearby part of the spine. In such cases, it may be
advantageous, when a target plate is used, to leave the target in
place during the robotic disc positioning, such that the target
then has the multiple functions of being the co-ordinate reference
frame for the fluoroscopic images, and for the robot guidance
control. Alternatively and preferably, when marker balls on K-wires
are used as the spatially defining targets, they can also be used
as the spatial reference for relating the robot guidance control
system to the vertebra location in the fluoroscope images.
According to the previously described embodiments, the registration
procedure is used to relate the predetermined disc position onto
the fluoroscope images so that the surgeon can position the disc
over a virtual disc image implanted on the fluoroscope images.
According to yet further preferred embodiments of the present
invention, the registration procedure is performed as previously,
with the optimum preoperatively defined disc position registered
with the fluoroscope image data. However, according to this
embodiment, this position is defined intraoperatively by aiming a
physical pointer mounted in a known position relative to the
vertebrae, at the correct point for the disc positioning in a
fluoroscope image, so that the surgeon can then use the physical
pointer to position the disc, without the need to look at more
fluoroscope images. This method is preferably implemented by
attaching an adjustable pointer to the K-wires, the pointer being
adjusted manually after registration to point at the predefined
disc location.
There is therefore provided in accordance with a preferred
embodiment of the present invention, a system for intraoperatively
placing an artificial disc at a predetermined position between two
vertebrae of a subject, the system comprising: (i) a computing
system having a storage medium including a set of preoperative CT
data showing the two vertebrae and the predetermined position of
the disc between them, (ii) at least one target having radio-opaque
markers adapted to be attached to at least one of the vertebrae to
define the position of the vertebra in at least one intra-operative
fluoroscope image of the subject, (iii) a tool for intra-operative
insertion of the artificial disc, and (iv) a registration system
for relating the at least one intra-operative fluoroscope image to
the set of preoperative CT data, such that the predetermined disc
position is displayed in the at least one fluoroscope image of the
subject, thereby enabling intraoperative placement of the
artificial disc in the predetermined disc position.
In the above mentioned system, the predetermined position of the
disc is preferably obtained from predefined geometrical information
about the position. This predetermined position of the disc may
preferably be obtained by adjusting the disc position in a model
obtained from the preoperative CT data, such that facet joints
between the vertebrae are in minimally stressed positions. The at
least one target is preferably a three dimensional radiographic
target. Alternatively and preferably, the at least one target is at
least two pins attached to each of the vertebrae, each of the pins
comprising at least two radio-opaque markers disposed at known
positions along the pins, such that the pins define the three
dimensional position of the vertebrae in the fluoroscope images of
the subject.
According to even another preferred embodiment, the at least one
target is at least one pin attached to each of the vertebra, each
of the pins comprising at least three radio-opaque markers disposed
at known positions along the pins, such that the pins define the
three dimensional position of the vertebrae in the fluoroscope
images of the subject. In those embodiments using a target, the
system preferably further comprises at least two pins attached to
each of the vertebrae, each of the pins comprising at least two
radio-opaque markers disposed at known positions along the pins,
such that the pins define the three dimensional position of the
vertebrae in the fluoroscope images of the subject, such that the
target may be removed to allow intra-operative placement of the
disc in the predetermined position. Furthermore, in those
embodiments using a target, the system may alternatively preferably
further comprise at least one pin attached to each of the vertebra,
each of the pins comprising at least three radio-opaque markers
disposed at fixed positions along the pins, such that the pins
define the three dimensional position of the vertebrae in the
fluoroscope images of the subject, such that the target may be
removed to allow intra-operative placement of the disc in the
predetermined position
In any of the above described systems, the insertion tool may
preferably be a manually operated tool or a robotically operated
tool.
There is further provided in accordance with yet another preferred
embodiment of the present invention, a method of intraoperatively
positioning an artificial disc between two vertebrae of a subject,
the method comprising the steps of: (i) generating from a
preoperative set of CT data, a CT model showing the vertebrae, (ii)
predetermining a position for the disc between the vertebrae, and
defining the position in the model, (iii) attaching at least one
target to one of the vertebrae, (iv) generating at least one
fluoroscope image of the subject, such that the three dimensional
position of the one of the vertebrae is defined in the at least one
fluoroscope image by means of the at least one target, (v)
registering the at least one fluoroscope image of the subject with
the CT model, such that a rendering of the disc in its
predetermined position is shown on the at least one fluoroscope
image, and (vii) using the at least one fluoroscope image to
position the disc intra-operatively such that it can be disposed in
the predetermined disc position.
In the above described method, the artificial disc may preferably
be disposed in the predetermined disc position by ensuring that the
intra-operative position in the fluoroscope image essentially
coincides with the display of the predetermined disc position. The
predetermined disc position may be obtained either from predefined
geometrical information about the optimum position, or by adjusting
the disc position in the CT model such that facet joints between
the vertebrae are in minimally stressed positions. The at least one
target may preferably be a three dimensional radiographic target.
The target may preferably be at least two pins attached to each of
the vertebrae, each of the pins comprising at least two
radio-opaque markers disposed at known positions along the pins,
such that the pins define the three dimensional position of the
vertebrae in the fluoroscope images of the subject. Alternatively
and preferably, the at least one target may be at least one pin
attached to each of the vertebra, each of the pins comprising at
least three radio-opaque markers disposed at fixed positions along
the pins, such that the pins define the three dimensional position
of the vertebrae in the fluoroscope images of the subject.
In accordance with still another preferred embodiment of the
present invention, there is provided a method as described above,
and further comprising the steps of: (viii) providing at least four
pins, each of the pins comprising at least two radio-opaque markers
disposed at known positions along their length, (ix) attaching at
least two of the pins to each of the vertebrae, such that the pins
define the three dimensional position of the vertebrae in the at
least one fluoroscope image, (x) utilizing the relationship between
the known positions of the target and the pins to compute a
transformation between the position of the target and the pins, and
(xi) removing the target to facilitate access to the vertebrae.
There is further provided in accordance with still another
preferred embodiment of the present invention, a method as
described above, and further comprising the steps of: (viii)
providing at least two pins, each of the pins comprising at least
three radio-opaque markers disposed at known positions along the
pins, (ix) attaching at least one of the pins to each of the
vertebrae, such that the pins define the three dimensional position
of the vertebrae in the at least one fluoroscope image, (x)
utilizing the relationship between the known positions of the
target and the pins to compute a transformation between the
position of the target and the pins, and (xi) removing the target
to facilitate access to the vertebrae.
In accordance with a further preferred embodiment of the present
invention, there is also provided a system for intraoperatively
placing an artificial disc at a predetermined position between two
vertebrae of a subject, the system comprising: (i) a computing
system having a storage medium including a set of preoperative CT
data showing the two vertebrae and the predetermined position of
the disc between them, (ii) at least one target having radio-opaque
markers adapted to be attached to at least one of the vertebrae to
define the position of the vertebra in at least one intra-operative
fluoroscope image of the subject, (iii) a jig adapted to be
attached to at least one of the vertebrae and supporting a
reproducibly alignable pointer, and (iv) a registration system for
relating the at least one intra-operative fluoroscope image to the
set of preoperative CT data, such that the predetermined disc
position and the pointer are displayed in the at least one
fluoroscope image of the subject, thereby enabling use of the
pointer for intraoperative placement of the artificial disc in its
predetermined position without the need to view a fluoroscope
image.
There is provided in accordance with yet a further preferred
embodiment of the present invention, a method of operatively
positioning an artificial disc between two vertebrae of a subject,
the method comprising the steps of: (i) generating from a
preoperative set of CT data, a CT model showing the vertebrae, (ii)
predetermining a position for the disc between the vertebrae and
defining the position in the model, (iii) attaching at least one
target to one of the vertebrae, (iv) generating at least one
fluoroscope image of the subject, such that the three dimensional
position of the one of the vertebrae is defined in the at least one
fluoroscope image by means of the at least one target, (v)
registering the at least one fluoroscope image of the subject with
the CT model, such that a rendering of the disc in its
predetermined position is shown on the at least one fluoroscope
image, (vi) attaching a jig to the vertebrae, the jig comprising a
pointer which can be reproducibly aligned, (vii) viewing the
pointer on at least one fluoroscope image and aligning the pointer
such that it touches a predetermined part of the rendering of the
disc, and (viii) using the pointer to position the disc
intra-operatively, such that the disc can be disposed in the
predetermined disc position without the need to view a fluoroscope
image.
There is even further provided in accordance with a preferred
embodiment of the present invention, a system for intraoperatively
inserting a surgical tool into a predetermined position at a
surgical site of a subject, the system comprising: (i) a computing
system having a storage medium including a set of preoperative CT
data showing the surgical site and the predetermined position of
the surgical tool, (ii) at least one target having radio-opaque
markers adapted to be attached to a feature of the subject at the
surgical site to define the position of the feature in at least one
intra-operative fluoroscope image of the subject, and (iii) a
system for registering the at least one intra-operative fluoroscope
image to the set of preoperative CT data, such that the
predetermined position of the surgical tool is displayed in at
least one fluoroscope image of the subject, thereby enabling
intraoperative insertion of the surgical tool into the
predetermined position.
Furthermore, in accordance with yet another preferred embodiment of
the present invention, there is provided a method of
intraoperatively inserting a surgical tool into a predetermined
position at a surgical site of a subject, the method comprising the
steps of: (i) generating from a preoperative set of CT data, a CT
model showing the surgical site, (ii) predetermining a position for
insertion of the surgical tool into the predetermined position at
the surgical site, and defining the position in the model, (iii)
attaching at least one target to a feature of the subject at the
surgical site, (iv) generating at least one fluoroscope image of
the feature such that the three dimensional position of the feature
is defined in the at least one fluoroscope image by means of the at
least one target, (v) registering the at least one fluoroscope
image of the subject with the CT model, such that the predetermined
position of the surgical tool is displayed on the at least one
fluoroscope image, and (vi) using the at least one fluoroscope
image to insert the surgical tool intra-operatively such that it
can be disposed in the predetermined position.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood and appreciated more fully
from the following detailed description, taken in conjunction with
the drawings in which:
FIGS. 1A and 1B illustrate the facet joints of a pair of
neighboring vertebrae, and the way in which they operate during
spinal bending forwards and backwards;
FIG. 2 illustrates schematically a model of the patient's spine,
generated using data from preoperative CT scanning of the
vertebrae;
FIGS. 3 and 4 are respectively anterior and lateral views of the
spinal model of FIG. 2;
FIGS. 5 and 6 are fluoroscope images taken of the spinal region
where the degenerated disc is being replaced, FIG. 5 being an AP
image, while FIG. 6 is a 60.degree. obliquely acquired LT
image;
FIG. 7 is a schematic example of a 3-dimensional target plate for
use in the registration process;
FIG. 8 is an AP fluoroscope image of the operation site, with a
virtual image of the replacement disc implanted onto the real life
fluoroscope image;
FIG. 9 is a schematic illustration of the use of a pointer attached
to a K-wire, and, using the system of the present invention,
aligned to the predetermined position in which the artificial disc
is to be inserted;
FIGS. 10A and 10B are schematic illustrations showing the
positioning of a kyphoplasty needle in a subject's vertebra through
the pedicle region, using the system and methods of the present
invention;
FIG. 11 illustrates the use of the hardware elements of the present
invention in performing an artificial disc insertion into the L5-S1
disc space; and
FIG. 12 illustrates schematically the control and computing
elements of the system of the present invention, according to one
preferred embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Reference is now made to FIG. 2, which illustrates schematically a
model of the patient's spine, generated using data from
preoperative CT scanning of the vertebrae. The model is built such
that the separate vertebrae can be mutually virtually moved to
enable insertion of the artificial disc between the desired
vertebrae. The vertebrae are moved virtually by any of the
generally available computer-based techniques, the most convenient
being by use of the computer mouse, with the system software
translating mouse movements to vertebral position movements. The
vertebrae can be manipulated in all directions, both vertically,
laterally and angularly, to enable correct insertion of the
selected disc. The model takes into account the disc size and
vertebral inclination. This is illustrated in FIGS. 3 and 4, which
are respectively anterior and lateral views of the spinal model,
showing how the artificial disc 30 is inserted virtually between
the relevant adjacent vertebrae 32, 34.
The optimum AP position of the disc within the plane between the
vertebrae must now be defined. This is done using the geometrical
centers of rotation of the neighboring vertebrae. According to a
currently widely accepted view, the preferred position is
considered to be 2 mm dorsal to the sagittal vertebral midline, and
laterally on the midline of the vertebral body. It is possible that
this determination, though a good generally applicable rule of
thumb, does not take into account individual features of the
personal spinal anatomy of the patient being treated. According to
a preferred embodiment of the present invention, the system enables
the disc to be virtually maneuvered within its inter-vertebral
space until the facet joints, as viewed on the virtual CT images of
the model of the spine, are in the optimum bio-mechanical position,
closest to their natural stance, as compared to that of the facet
joints of neighboring vertebrae. This experimentally determined
position takes into account any actual anatomical anomalies of the
neighboring vertebrae to the new disc. This position should result
in the minimum stress and loading of the facet joints, such that
the success and the recovery rate of the procedure, as determined
by recovered, pain-free mobility, should be optimized. This is in
contrast to previously used procedures, where the standard location
used for positioning the disc may not be the optimum for
successful, pain-free motion recovery.
In practice, the correct disc configuration is chosen from a
library of optional discs, according to the type, lateral size,
angle and thickness required. The orientation, position and angle
of the disc endplates is calculated, and, using a virtual
representation of the disc size chosen, the disc endplates are
placed on the operation plan by inserting the disk virtually into
the spinal CT model. The vertebra can be moved apart and
re-oriented in the model in order to obtain the correct positioning
for the disc chosen, either according to a conventionally accepted
standard position configuration, or by viewing the stress or
distortion generated on the facet joints. The operation plan,
showing the planned vertebrae orientation/position is analyzed,
preferably including the spine orientation during motion, and this
then completes the creation of the preoperative plan, which is
stored in the system for later intra-operative use.
Hardware elements of the system are utilized during the operation
itself. The procedure is first described using a removable target
plate and K-wires for position determination. Reference is first
made to FIGS. 5 and 6, which are fluoroscope images taken of the
spinal region where the degenerated disc is being replaced. FIG. 5
is an AP image, while FIG. 6 is a 60.degree. obliquely acquired
image, though a lateral view could equally well be used. The outer
set of fiduciary balls 50 seen in the images are from the
conventional C-arm dewarping jig, used to calibrate the C-arm, as
is known in the art. The closely spaced rectilinear array of balls
52 in the vicinity of the neighboring vertebrae is from a three
dimensional registration target, used to define the co-ordinate
system of the real time fluoroscope images. These fluoroscope
images are first registered with the preoperative CT images on
which the planning was performed, preferably by means of image
processing procedures to match vertebral anatomic features between
the two sets of images, as is known in the art. The preoperative CT
images can thus be aligned with any real life fluoroscope image
taken of the patient in real time during the surgical procedure,
the fluoroscope image orientation and position being determined
initially by means of the target. The target is preferably mounted
on one of the vertebrae adjacent the disc to be replaced. Such a
target can take a number of alternative forms, and preferably
contains two separated planes of radio-opaque fiduciary marker
balls, with a known geometric relationship between the two planes.
A schematic example of such a target plate is shown in FIG. 7.
In each of FIGS. 5 and 6, four K-wires 54 can be seen, two inserted
into each of the disc-adjacent vertebrae. K-wires, or equivalent
devices such as Steinman pins, are conventionally used during
anterior surgical exposure of the vertebrae, in order to retract
the vasculature and soft tissues from the site of the disc. The
K-wires of the embodiments of the system of the present invention
shown in FIGS. 5 and 6 differ from conventional K-wires in that
they have two spatially spaced balls on the lengths of the shafts,
close to the insertion end. Knowledge of the distance between the
positions of the balls on the shafts is not necessary, though it
can be used to increase the accuracy of the registration process.
Therefore, besides their above-mentioned use in the surgical
procedure as simple pins, the K-wires of the present invention can
be used to provide 3-dimensional positional data relating to the
vertebrae. This function will be described below. Although the
K-wires are shown with 2 fiduciary balls per wire, it is to be
understood that a larger number of balls can be used per wire, such
that the redundant data so provided enables a higher accuracy
coordinate registration process. Alternatively and preferably,
since the minimal number of spatial marker points required to
define a three-dimensional co-ordinate system is three, it is
possible to use a single pin in each vertebra, each pin having
three spatial markers whose mutual positions are known. In this
manner, not all of the ancillary surgical hardware required for use
in the operation, such as the retracting pins mentioned above, need
necessarily be associated with the marker function, since only one
marker pin per vertebra is required. Additionally, as mentioned
hereinabove, it is possible to use K-wires with less fiducial
marker information, such a K-wires with only one ball, or K-wires
without any marker balls, since the K-wire shape itself and its
alignment can be used as fiducial marker information. The number of
K-wires required per vertebra is determined according to the amount
of fiducial data associated with each wire.
Since the vertebrae can move relative to each other, each vertebra
whose position is important to the procedure, which generally means
the two vertebrae either side of the replacement disc, requires its
own set of K-wires to define its position in the fluoroscope
images. In those surgical procedures where K-wires are not used,
the operating table mounted retractors can be equipped with
markers, and used for providing the spatially defined data for use
in the registration processes. The assumption is made that there is
no significant relative motion between the retractors and the
vertebra, though this may limit the accuracy of a procedure using
markered retractors.
The elements of the system of the present invention are utilized in
this first preferred embodiment according to the following
procedure. Using the target mounted on one of the vertebrae, the
position and orientation (pose) of the X-ray imaging source
relative to the target, and hence relative to the vertebra, is
calculated, in the manner known in the art for such imaging
systems. Once the source position is known, then from the imaged
positions of the balls on the K-wires, the co-ordinate
transformation between the target and the K-wires can be
calculated. Once this transformation is known, then the target
itself may be removed, and any further procedures can be carried
out based on the now known positional information using the K-wire
ball positions. The target is preferably removed, since the very
limited space within the operation site would make it impossible to
insert and manipulate the new disc if the target was in the way.
The target could be held on an extension arm to avoid this problem,
but this is less desirable since a long extension arm would add to
the positional error. According to this first embodiment, the use
of the special K-wires of the present invention therefore enables
the real time fluoroscope images to be correlated with the
preoperative CT scanned data, without the continued presence of a
target plate during the surgical procedure.
According to a second preferred embodiments of the present
invention, it is also possible to perform the disc insertion
without removing the target plate, and hence without the use of the
special K-wire markers, or special retractor markers. Where
conditions are such that the target plate can remain in situ
without disturbing the insertion procedure and the surgeon's field
of view, and yet still provides a stable and accurate reference
source, this embodiment enables the use of a simpler registration
procedure.
According to a third preferred embodiment of the present invention,
it is also possible to perform the disc insertion procedure without
use of a target plate at all, by relying only on the special K-wire
markers or special retractor markers to provide the data required
regarding the position and orientation of the vertebrae. The K-wire
positional data obtained from any fluoroscope image is used to
determine any movement of the vertebrae between successive
fluoroscope images. Comparison of this data then enables the
position of any vertebra to be referenced back to the position of
the first fluoroscope image, which itself was registered to the
preoperative CT images, preferably by means of feature comparison,
as explained hereinabove. Thus, any subsequent fluoroscope image
can undergo co-ordinate transformation to the CT image co-ordinate
system, such that the subsequent fluoroscope images can be
displayed superimposed on the CT preoperative image, with the
desired virtual disc position, as originally positioned on the
virtual CT model of the spinal region of interest of FIGS. 3 and 4,
but now shown on the real time, intraoperative fluoroscope
image.
Reference is now made to FIG. 8, which is an AP fluoroscope image
of the operation site, showing the two adjacent vertebrae 80, 81
between which the artificial disc 82 is to be inserted. Implanted
onto the real life fluoroscope image is a virtual image of the
desired disc, whose position is the optimized position, determined
from the preoperative planning using the CT spinal model of FIGS. 3
and 4. This virtual disc then defines the optimum position of the
real life disc which the surgeon has to insert, and is used as a
guide for the surgeon as he manipulates the disc into place, until
its fluoroscope image exactly covers the outline of the optimally
positioned virtual disc from the CT scans. As a result of the
preliminary registration procedure, regardless of which of the
above mentioned procedures is used, the surgeon can view the real
life images from differently oriented fluoroscope images, with the
virtual disc displayed in the images in its planned intended
position, such that he can position the disc correctly and
accurately in both directions, fine tuning the final position by
successive viewing of the disc positioning from different
directions.
According to further preferred embodiments of the present
invention, it is also possible to use a surgical robot to position
the replacement disc into position. In this embodiment, the robot
base plate is registered relative to the vertebrally fixed target,
such as is described in U.S. Pat. No. 6,837,892, and in co-pending
International Published Applications No. WO2003/105,659 and
WO2005/032325, all hereby incorporated by reference, each in its
entirety. The robot may be mounted either directly on one of the
bones in the vicinity, or on the operating table adjacent to the
patient, who then has to be immobilized. The transformation between
the target plate and the special K-wires is then performed, such
that the robot position is then known relative to the K-wires. The
target plate may then be removed and the robot utilized to insert
the disc using the appropriate tool, into a position determined
preoperatively on the CT model, and now known to the spatial
control system of the robot from the registration procedure. In
such cases, and if appropriate from the specific surgical
configuration, the K-wires can be dispensed with, and the target
used throughout the procedure, including during the robotic disc
positioning. The target then has the multiple functions of being
the co-ordinate reference frame for the CT, for the fluoroscopic
images and for the registration between them, for the virtual disc
(as in fact already defined in the CT image), and for the robot
guidance control. Alternatively and preferably, in those
embodiments where a target plate is not used, and the registration
is performed directly using the marked K-wires, the robotic
placement is performed against the K-wire positions only.
Reference is now made to FIG. 9 which is a schematic illustration
of the use of a pointer 90 attached in a known manner to the
neighboring vertebrae, to assist the surgeon in positioning the
artificial disc 91, according to further preferred methods of the
present invention. In the illustration shown, the pointer 90 is
carried in a sleeve 92 attached rigidly to two K-wires 93, 94
inserted into a neighboring vertebra. The pointer can preferably be
adjusted within the sleeve to a predetermined position. As an
alternative to use of such a sleeve and K-pins, any other suitable
jigging arrangement which spatially defines the pointer position
relative to the neighboring vertebra, can equally well be used in
this embodiment. The system uses the same preoperative CT imaging
and planning as in the previously described embodiments. As
previously, the optimum predetermined position of the disc is
implanted onto a fluoroscope image of the vertebrae of the subject
after registration, and the surgeon then brings the pointer to a
position between the vertebrae, such that its tip defines in real
space, where a predetermined feature of the disc, such as the
forward-most edge, is to be positioned. Once this relationship
between the pointer and the optimum disc position has been
established, no further fluoroscope images need be taken, thus
significantly reducing the level of radiation used during the disc
positioning procedure. The surgeon simply inserts the disc until it
is located in the predetermined position relative to the tip of the
pointer. Since the lateral position can often be accurately judged
by the surgeon visually, the more critical positioning operation is
the A-P position. In practical use, the pointer can be pre-aligned
using the CT and first fluoroscopic image, so that its tip points,
according to one preferred embodiment, to where the forward edge of
the disc in its optimum position should be. The pointer is then
withdrawn so that the disc can be inserted to close to its correct
insertion depth, and the pointer reinserted in the sleeve to its
predetermined position to see whether the disc is already in the
correct position. This process can be repeated iteratively until
the optimum position is achieved. Although the use of one pointer
may provide sufficient accuracy to position the disc in both planar
directions between the vertebra, more accuracy may be achieved
using two such pointers, preferably with one defining the lateral
position, and one the A-P position. By use of these methods of the
present invention, the level of radiation used during the disc
positioning procedure is significantly reduced.
Reference is now made to FIGS. 10A and 10B which illustrate
schematically how, according to a further preferred embodiment of
the present invention, the system and methods of the present
invention can be used for the accurate positioning of a kyphoplasty
needle 100 inserted into a subject's vertebra 102 through the
pedicle region. FIG. 10A shows a schematic axial CT image of a
vertebra with a kyphoplasty needle inserted into the vertebral body
from an extrapedicular direction. As is evident from the axial
view, the surgeon requires great skill in order to ensure that the
needle follows the desired path. Such an axial view is not
generally available using a C-arm mounted fluoroscope system, and
the surgeon must rely on AP or other laterally angled fluoroscope
images for intra-operative guidance. FIG. 10B is a single oblique
fluoroscopic image of the same procedure, showing the path of the
needle into the vertebral body.
According to this preferred embodiment, the planned entry path of
the needle is determined using preoperatively obtained CT images,
and this optimum path is saved in the system memory. During the
surgical procedure, a target with radio-opaque features is attached
to the vertebra to be treated. As previously described, this target
can be a conventional three-dimensional target plate, or one or
more special marker attached K-wires inserted into the vertebra, or
any other method which provides three dimensional definition of the
position of the vertebra in the fluoroscope images. The fluoroscope
images with the marker positions are registered to the preoperative
CT image set, using image comparison as is known in the art, and a
virtual image of the desired needle position and orientation can
then be projected from the CT data, onto any fluoroscope image
taken intra-operatively. As shown schematically in FIG. 10B, this
desired path could preferably be marked as a dotted or colored line
103, so that it is clearly distinguishable from the image features.
During the procedure, the surgeon can then view the progress of the
needle insertion on the fluoroscope images, and can verify that the
needle is following the desired path indicated on the fluoroscope
image. In order to ensure correct adherence to the desired path,
lateral and A-P images, or oblique images need to be viewed by the
surgeon.
This procedure, according to the methods of the present invention,
can be used for increasing the positioning accuracy for any
surgical insert or tool which is amenable to the construction of a
preoperative CT model of the surgical site and the definition
thereon of the optimum position for the surgical insert or tool,
and the registration of this CT model to intra-operatively
generated fluoroscope images showing the actual progress of the
insert or tool position, together with the predetermined optimum
position.
Reference is now made to FIG. 11, which illustrates the use of the
hardware elements of the present invention in performing an
artificial disc insertion into the L5-S1 disc space. The special
K-wires of the present invention 110, with the marker balls on
their shafts are shown inserted into the vertebrae, together with
the three dimensional target 111, aligned such that it will be
readily imaged in the fluoroscopic images of the region, which are
taken using the schematically shown X-ray source 112 and camera
113. Once the registration to the special K-wire features has been
performed, the target may be removed so that it does not impede the
surgeon's view of the region. The target 111 in FIG. 11 is shown
smaller than its preferable size, in order not to occlude details
of the drawing. The artificial disc 114 is shown being inserted
between the vertebrae using an insertion rod 115. The whole of the
process is viewed on the fluoroscope images generated by the X-ray
C-arm source and camera.
According to further preferred embodiments, the disc could be
guided into position by means of a surgical robot, whose control
system coordinates are registered to those of the preoperative CT
scans, such that the robot can guide the disc into a predetermined
position without any, or with minimal surgeon intervention. The
robot could be either floor or bed mounted, or bone mounted, as is
known in the art.
Reference is now made to FIG. 12, which illustrates schematically
the control and computing elements of the system of the present
invention. The preoperative CT data is stored in a storage medium
121, from where it can be transferred to the spine model generator
122 for building the virtual spinal model for use in planning the
disc insertion position. Once the disc position has been
determined, the registration processor 123 is actuated, to relate
the coordinate system of the preoperative CT images, to that of the
fluoroscope images, preferably by means of image feature
comparison. Finally, the disc insertion position determined in the
spine model generator is implanted onto the fluoroscope images
displayed on the fluoroscope display unit 124, such that the
surgeon can compare the actual disc position with the intended disc
position on screen. The whole process and the computing steps are
overseen by means of the system computer 120.
It is appreciated by persons skilled in the art that the present
invention is not limited by what has been particularly shown and
described hereinabove. Rather the scope of the present invention
includes both combinations and subcombinations of various features
described hereinabove as well as variations and modifications
thereto which would occur to a person of skill in the art upon
reading the above description and which are not in the prior
art.
* * * * *
References